Method and apparatus for coding video using merging candidate list according to block division

ABSTRACT

The present invention relates to block merging according to block split among video coding techniques, and a method and an apparatus for coding and decoding a video, in which in generating and modifying a block merging list, spatial merging candidate blocks of the block merging list are changed according to a split type and order of a current coding unit.

TECHNICAL FIELD

The present invention relates to an image processing technology and,more particularly, to a method and apparatus modifying a mergingcandidate list according to a block split in a video compressiontechnology.

BACKGROUND ART

Recently, as the demand for high resolution and high definition videoincreases, there is a need for a high efficiency video compressiontechnology for next generation video services. Based on such a need,ISO/IEC MPEG and ITU-T VCEG, which jointly standardized H.264/AVC andHEVC video compression standards, formed the Joint Video ExplorationTeam (JVET), and has been conducting study and research to enact a newvideo compression standard since October 2015.

In video compression technology, a block split structure refers to aunit for coding and decoding, and a unit to which main technologies forcoding and decoding such as prediction and transformation are applied.As video compression technology evolves, a block size for coding anddecoding is gradually increasing, and a block split form supports morevarious split forms. In addition, video compression is performed usingnot only the unit for coding and decoding but also a unit subdividedaccording to a role of the block.

In the HEVC standard, video coding and decoding are performed using aunit block subdivided according to the block split structure in aquadtree form and the role for prediction and transformation. Inaddition to the block split structure in the quadtree form, variousforms of the block split structure, such as Quadtree plus Binary Tree(QTBT) having a form that combines a quadtree and a binary tree, andMulti-Type-Tree (MTT) that combines a triple tree with the QTBT, havebeen proposed for improving video coding efficiency. Through the supportof such various block sizes and various forms of the block splitstructure, a single picture is split into a plurality of blocks so thatcoding unit information such as a coding mode corresponding to eachblock, motion information, and intra-frame prediction directioninformation is variously represented, whereby the number of bitsrepresenting this information greatly increases.

A proposed method to reduce the number of bits required to representeach split block is a block merge technology, which is a technology fortransmitting reference information on which neighboring blocks arereferred to instead of just using coding information about blocks, whichare spatially and temporally adjacent. For block merging, spatially andtemporally adjacent blocks are constructed as one merging candidate listaccording to a certain rule, and the technique of constructing such amerging candidate list is called a Derivation Process for mergecandidate list.

DISCLOSURE Technical Problem

In generating a merging candidate list of current coding and decodingtarget blocks, the objective of the present invention is to provide amethod and apparatus for improving coding efficiency compared toexisting video compression technologies by removing duplicate motioninformation in the merging candidate list and redundancy of syntax thatmay be caused by merging a target block with a current block

However, the technical problem to be achieved by the present exemplaryembodiment is not limited to the above technical problems, and othertechnical problems may exist.

Technical Solution

In order to solve the problem, a video coding method according to theexemplary embodiment of the present invention including: generating ablock merging candidate list for motion compensation of a current codingunit, wherein the generating the block merging candidate list includes:adding spatial neighboring merging candidate blocks of the currentcoding unit to a merging candidate list; adding temporal neighboringmerging candidate blocks of the current coding unit to the mergingcandidate list; adding combined bi-directional merging candidates to themerging candidate list; and adding a zero motion merging candidate tothe merging candidate list.

In order to solve the problem, a video coding apparatus according to theexemplary embodiment of the present invention including: an interprediction unit generating a block merging candidate list for motioncompensation of a current coding unit, wherein, in order to generate theblock merging candidate list, the inter prediction unit adds spatialneighboring merging candidate blocks of the current coding unit to beadded to a merging candidate list, temporal neighboring mergingcandidate blocks of the current coding unit to be added to the mergingcandidate list, combined bi-directional merging candidates to be addedto the merging candidate list and a zero motion merging candidate.

In order to solve the problem, there is provided the video coding methodand apparatus according to the exemplary embodiment of the presentinvention, wherein, among the spatial neighboring merging candidateblocks of the current coding unit to be added to the merging candidatelist, a certain spatial neighboring merging candidate block is removedfrom the merging candidates, depending on a block split type of a codingunit, a coding order of a split coding unit, and a relation between asize of the split coding unit and a size of the spatial neighboringmerging candidate block.

In order to solve the problem, there is provided the video coding methodand apparatus according to the exemplary embodiment of the presentinvention, wherein, among the spatial neighboring merging candidateblocks of the current coding unit to be added to the merging candidatelist, a certain spatial neighboring merging candidate block is removedfrom the merging candidates, depending on a block split type of a codingunit, a coding order of a split coding unit, and a relation between asplit depth of the split coding unit and a split depth of the spatialneighboring merging candidate block.

In order to solve the problem, there is provided the video coding methodand apparatus according to the exemplary embodiment of the presentinvention, wherein, among the spatial neighboring merging candidateblocks of the current coding unit to be added to the merging candidatelist, a position of a certain spatial neighboring merging candidateblock is changed depending on a block split type of a coding unit, acoding order of a split coding unit, and a relation between a size ofthe split coding unit and a size of the spatial neighboring mergingcandidate block.

In order to solve the problem, there is provided the video coding methodand apparatus according to the exemplary embodiment of the presentinvention, wherein, among the spatial neighboring merging candidateblocks of the current coding unit to be added to the merging candidatelist, a position of a certain spatial neighboring merging candidateblock is changed depending on a block split type of a coding unit, acoding order of a split coding unit, and a relation between a splitdepth of the split coding unit and a split depth of the spatialneighboring merging candidate block.

In order to solve the problem, there is provided the video coding methodand apparatus according to the exemplary embodiment of the presentinvention, wherein, among the spatial neighboring merging candidateblocks of the current coding unit to be added to the merging candidatelist, a certain spatial neighboring merging candidate block is addeddepending on a block split type of a coding unit, a coding order of asplit coding unit, and a relation between a size of the split codingunit and a size of the spatial neighboring merging candidate block.

In order to solve the problem, there is provided the video coding methodand apparatus according to the exemplary embodiment of the presentinvention, wherein, in the spatial neighboring merging candidate blocksof the current coding unit to be added to the merging candidate list, acertain spatial neighboring merging candidate block is added dependingon a block split type of a coding unit, a coding order of a split codingunit, and a relation between a split depth of the split coding unit anda split depth of the spatial neighboring merging candidate block.

Advantageous Effects

The objective of the present invention is to provide a video codingmethod and apparatus for improving coding efficiency by removingduplicate motion information in a merging candidate list in a process ofgenerating the merging candidate list of coding and decoding targetblocks and redundancy of syntax that may be caused by merging a targetblock with a current block, in a video coding method and apparatussupporting various block sizes and various types of a block splitstructure.

According to an exemplary embodiment of the present invention, in theprocess of generating the merging candidate list of a block which issplit into two or more blocks, coding performance may be improved byremoving one or more merging candidates from the list according to acertain condition so as to prevent generation of redundant syntax causedby redundant motion information and merging.

DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram illustrating a configuration of a videoencoding apparatus according to an exemplary embodiment of the presentinvention.

FIG. 2 is a block diagram illustrating a configuration of a videodecoding apparatus according to the exemplary embodiment of the presentinvention.

FIG. 3 is a drawing illustrating a concept of a quadtree blockstructure, a coding unit, a prediction unit, and a transformation unitaccording to the exemplary embodiment of the present invention.

FIG. 4 is a drawing illustrating a concept of a QTBT block structure, abinary split type, and a binary split block index generated by binarysplitting according to the exemplary embodiment of the presentinvention.

FIG. 5 is a drawing illustrating a concept of an MTT block structure, asplit type, and a split block index generated by binary and triplesplitting according to the exemplary embodiment of the presentinvention.

FIG. 6 is a drawing illustrating an example in which spatial neighboringblocks used in generating a merging candidate list are constructeddifferently according to a split form of a current prediction unitaccording to the exemplary embodiment of the present invention.

FIG. 7 is a drawing illustrating an example of a case in which thespatial neighboring blocks used in generating the merging candidate listare identically constructed regardless of the split form of the currentcoding unit according to the exemplary embodiment of the presentinvention.

FIG. 8 is a drawing illustrating an example of the spatial neighboringblocks used in generating the merging candidate list of a second binarysplit block among blocks which are binary-split in a horizontaldirection according to the exemplary embodiment of the presentinvention.

FIG. 9 is a drawing illustrating an example of the spatial neighboringblocks used in generating the merging candidate list of a second binarysplit block among the blocks which are binary-split in a verticaldirection according to the exemplary embodiment of the presentinvention.

FIG. 10 is a drawing illustrating an example in which a position of thespatial merging candidate blocks is changed according to a split form ofa first binary split block to generate the merging candidate list of thesecond binary split block among the blocks which are binary-split in ahorizontal direction according to the exemplary embodiment of thepresent invention.

FIG. 11 is a drawing illustrating an example in which the position ofthe spatial merging candidate blocks is changed according to the splitform of the first binary split block to generate the merging candidatelist of the second binary split block among the blocks which arebinary-split in the vertical direction according to the exemplaryembodiment of the present invention.

FIG. 12 is a drawing illustrating an example in which the number of thespatial merging candidate blocks is increased according to the splitform of the first binary split block to generate the merging candidatelist of the second binary split block among the blocks which arebinary-split in the horizontal direction according to the exemplaryembodiment of the present invention.

FIG. 13 is a drawing illustrating an example in which the number of thespatial merging candidate blocks is increased according to the splitform of the first binary split block to generate the merging candidatelist of the second binary split block among the blocks which arebinary-split in the vertical direction according to the exemplaryembodiment of the present invention.

FIG. 14 is a drawing illustrating an example of the spatial mergingcandidate blocks of each of the split blocks among the blocks which aretriple-split in the horizontal direction according to the exemplaryembodiment of the present invention.

FIG. 15 is a drawing illustrating an example of the spatial mergingcandidate blocks of each of the split blocks among the blocks which aretriple-split in the vertical direction according to the exemplaryembodiment of the present invention.

FIG. 16 is a flowchart illustrating a removal of a spatial neighboringmerging candidate at a left side of a second split block among theblocks which are binary-split in the vertical direction according to theexemplary embodiment of the present invention.

FIG. 17 is a flowchart illustrating a removal of the spatial neighboringmerging candidate at an upper end of the second split block among theblocks which are binary-split in the horizontal direction according tothe exemplary embodiment of the present invention.

FIG. 18 is a drawing illustrating an example of merging blocks thatperform sub-block unit motion compensation among the spatial neighboringblocks used in generating the merging candidate list according to theexemplary embodiment of the present invention.

FIG. 19 is a flowchart illustrating a removal of the spatial neighboringmerging candidate at the upper end of the second split block among theblocks which are binary-split in the horizontal direction according tothe exemplary embodiment of the present invention.

FIG. 20 is a flowchart illustrating a removal of the spatial neighboringmerging candidate at the upper end of the second split block among theblocks which are binary-split in the vertical direction according to theexemplary embodiment of the present invention.

FIG. 21 is a flowchart illustrating generation of the merging candidatelist according to the exemplary embodiment of the present invention.

BEST MODE

As described above, a video coding method and apparatus according toexemplary embodiments of the present invention include generating ablock merging candidate list for motion compensation of a current codingunit, wherein the block merging candidate list generator includes:adding spatial neighboring merging candidate blocks of the currentcoding unit to the merging candidate list; adding temporal neighboringmerging candidate blocks of the current coding unit to the mergingcandidate list; adding combined bi-directional merging candidates to themerging candidate list; and adding a zero motion merging candidate tothe merging candidate list.

Hereinafter, exemplary embodiments of the present invention will bedescribed in detail with reference to the drawings accompanied in thisspecification so that those skilled in the art may easily implement thepresent invention. However, the present invention is not limited to theexemplary embodiments described herein and may be embodied in manydifferent forms. In addition, descriptions which are not necessary tounderstand the exemplary embodiments will be omitted in order to clearlyexplain the exemplary embodiments in the drawings, and analogouscomponents are rendered with analogous reference numbers throughout thedescription of the exemplary embodiments.

In the exemplary embodiments, an expression such as “connect(ed)” isintended to include not only “direct(ly) connect(ed)” but also“electrical(ly) connect(ed)” having a different component in the middle.In addition, throughout the specification, unless explicitly describedto the contrary, the word “comprise” and variations such as “comprises”or “comprising” will be understood to imply the inclusion of statedelements but not the exclusion of any other elements.

The term “step of performing ˜” or “step of ˜” used throughout thepresent specification does not mean the “step for ˜”. In addition, itwill be understood that, although the terms “first”, “second”, etc. maybe used herein to describe various elements, these elements should notbe limited by these terms. These terms are only used for the purpose ofdistinguishing one element from another element.

In addition, the components shown in the exemplary embodiments of thepresent invention are shown independently to represent characteristicfunctions which are different from each other, and do not mean that eachcomponent is made of separate hardware or one software component unit.That is, each component is described by listing each component forconvenience of description, and at least two of the components may becombined to form one component, or one component may be divided into aplurality of components to perform a function. The integrated andseparated exemplary embodiments of each of these components are alsoincluded within the scope of the present invention without departingfrom the spirit of the present invention.

In the various exemplary embodiments of the present invention describedherein below, the terms “˜ part”, “˜group”, “˜ unit”, “˜ module”, “˜block”, and the like mean a unit for processing at least one function oroperation, and may be implemented by a combination of hardware and/orsoftware.

In addition, a coding block refers to a processing unit of a set oftarget pixels on which coding and decoding are currently performed, andmay be used interchangeably as a coding block or a coding unit. Inaddition, the coding unit refers to the coding unit (CU), and may bereferred to comprehensively including the coding block (CB).

In addition, quadtree split refers that one block is split into fourindependent coding units, and binary split refers that one block issplit into two independent coding units.

Hereinafter, the video coding method and apparatus using a mergingcandidate list generation method based on the block split which isproposed according to the exemplary embodiments of the present inventionwill be described in detail.

Mode of Invention

FIG. 1 is a block diagram illustrating a configuration of a videoencoding method and apparatus according to an exemplary embodiment ofthe present invention.

The video coding method and apparatus according to the exemplaryembodiment may include: an inter prediction unit 120; an intraprediction unit 125; a subtractor 130; a transform unit 140; aquantization unit 150; an entropy encoding unit 160; an inversetransform unit 145; an inverse quantization unit 155, an adder 135; anin-loop filter unit 180; and a reconstruction picture buffer 190.

The inter prediction unit 120 generates a prediction signal byperforming motion prediction using an input image 110 and areconstructed image stored in the reconstruction picture buffer 190.

The intra prediction unit 125 generates a prediction signal byperforming spatial prediction using A pixel value of pre-reconstructedneighboring block that is spatially adjacent to a current block to becoded.

The subtractor 130 generates a residual signal by using the input imageand the prediction signal generated by the inter prediction unit 120 orthe intra prediction unit 125.

The transform unit 140 and the quantization unit 150 generate quantizedcoefficients by performing transformation and quantization on theresidual signal generated by the subtractor 130.

The entropy encoding unit 160 outputs a bitstream by performing entropycoding on coding information such as syntax elements and quantizedcoefficients defined in the video compression standards.

The inverse transform unit 145 and the inverse quantization unit 155receive the quantized coefficients, perform inverse quantization andinverse transformation in order, and generate the reconstructed residualsignal.

The adder 135 generates a reconstructed signal by using the predictionsignal, generated by the inter prediction unit 120 or the intraprediction unit 125, and the reconstructed residual signal.

The reconstructed signal is transmitted to the in-loop filter unit 180to generate a final reconstructed signal by applying one or more in-loopfilters such as a deblocking filter, a Sample Adaptive Offset (SAO), andan Adaptive Loop Filter (ALF), and a final reconstructed signal isstored in the reconstruction picture buffer 190. The reconstructedsignal stored in the reconstruction picture buffer 190 may be used asreference signal by the inter prediction unit 120.

FIG. 2 is a block diagram illustrating a configuration of a videodecoding apparatus and method according to the exemplary embodiment ofthe present invention.

The video decoding apparatus and method according to the exemplaryembodiment may include: an entropy decoding unit 210; an inversequantization unit 220; an inverse transform unit 230; an intraprediction unit 240; an inter prediction unit 250; an adder 260; anin-loop filter unit 270; and a reconstruction picture buffer 280.

The entropy decoding unit 210 decodes an input bitstream 200 and outputsdecoding information such as syntax elements and quantized coefficients.

The inverse quantization unit 220 and the inverse transform unit 230receive the quantized coefficients, perform inverse quantization andinverse transformation in order, and output a residual signal.

The intra prediction unit 240 generates a prediction signal byperforming spatial prediction using a pixel value of pre-decodedneighboring block that is spatially adjacent to the current block to bedecoded.

The inter prediction unit 250 generates a prediction signal byperforming motion compensation using the motion vector extracted fromthe bitstream and a reconstructed image stored in the reconstructionpicture buffer 280.

The prediction signal which is output from the intra prediction unit 240and the inter prediction unit 250 is added to the residual signalthrough the adder 260 to generate the reconstructed signal.

The reconstructed signal is transmitted to the in-loop filter unit 270to generate the final reconstructed signal by applying one or morein-loop filters such as the deblocking filter, the Sample AdaptiveOffset (SAO), and the Adaptive Loop Filter (ALF), and the finalreconstructed signal is stored in the reconstruction picture buffer 190.The reconstructed signal stored in the reconstruction picture buffer 190may be used as the reference signal by the inter prediction unit 120.

FIG. 3 is a drawing illustrating a concept of a quadtree blockstructure, a coding unit, a prediction unit, and a transformation unitaccording to the exemplary embodiment of the present invention.

The quadtree block structure according to the exemplary embodimentincludes a block which is split into four sub-blocks, wherein each ofthe four sub-blocks which are split is split again into four sub-blocksas one independent block.

The Coding Unit (CU) may be used as a block unit using the quadtreeblock split structure according to the exemplary embodiment, and theblock at the uppermost level of a CU quadtree block structure is calleda Coding Tree Unit (CTU). As an example of the CU quadtree blockstructure, when one 64×64 CTU 310 is split into CUs at the low level asillustrated in FIG. 3, the corresponding quadtree may be represented byquadtree split information 340. The 64×64 CTU 310 may be split into four32×32 CUs, and each of the four 32×32 CUs may be independently splitagain into four CUs, or may maintain a block size without being split.

Information on whether the quadtree blocks are split according to theexemplary embodiment may be represented in a form of flags of 0 and 1,and may be represented as 0 when not split, and as 1 when split.However, in the block split unit at the lowermost level, the informationabout whether the corresponding block is split is not necessary to besignaled.

One coding unit (CU) according to the exemplary embodiment may besubdivided into a Prediction Unit (PU) which is a unit for predictionand a Transformation Unit (TU) which is a unit for transformationaccording to roles which are performed.

The PU, which is a unit for prediction according to the exemplaryembodiment, may have a total of eight forms, and when represented usingan arbitrary length N, the PU may have block sizes of 2N×2N, 2N×N, N×2N,N×N, 2N×nU, 2N×nD, nL×2N, and nR×2N. The 2N×nU means a form which issplit into 2N×(½) N size block and 2N×(3/2) N size block, and the 2N×nDmeans a form which is split into 2N×(3/2) N size block and 2N×(½) N sizeblock. In addition, nL×2N means a form which is split into (½) N×2N sizeblock and (3/2) N×2N size block, and nR×2N means a form which is splitinto (3/2) N×2N size block and (½) N×2N size block.

The TU, which is a unit for transformation, according to the exemplaryembodiment may be split into four TUs at the low level by using thequadtree block split in the same manner as the CU. Whether the quadtreeis split for the TU may also be represented in the form of the flags of0 and 1, and may be represented as 0 when not split, and as 1 whensplit. However, in the TU split unit at the lowermost level, theinformation about whether the corresponding block is split is notnecessary to be signaled.

FIG. 4 is a drawing illustrating a concept of a QTBT block structure, abinary split type, and a binary split block index generated by binarysplitting according to the exemplary embodiment of the presentinvention.

When there is a block 410 which is split using the QTBT block splitaccording to the exemplary embodiment, the block 410 may be split intofour square blocks by using the quadtree block split. In addition, inthe QTBT block split, a binary block split may be started from a leafnode of the quadtree generated by the quadtree block split.

In FIG. 4, a first quadtree split block of the block 410 at theuppermost level corresponds to the leaf node of the quadtree andrepresents an exemplary embodiment in which binary block splitting 411in the vertical direction is performed. The first binary split block,which is split by performing the binary block splitting 411 in thecorresponding vertical direction, represents an exemplary embodiment inwhich binary block splitting 415 in the vertical direction is performedonce again.

A second quadtree split block of the block 410 at the uppermost levelcorresponds to the leaf node of the quadtree and represents an exemplaryembodiment in which binary block splitting 412 in the horizontaldirection is performed. The two binary split blocks, which are split byperforming the corresponding binary block splitting 412 in thehorizontal direction, represents an exemplary embodiment in which noadditional binary split is performed.

A third quadtree split block of the block 410 at the uppermost levelrepresents an exemplary embodiment in which one additional quadtreeblock splitting 413 is performed to generate four quadtree split blocksat the low level. The first quadtree split block, among the fourquadtree split blocks at the low level generated as above, correspondsto the leaf node of the quadtree and represents an exemplary embodimentin which binary block splitting 416 in the vertical direction isperformed. The second binary split block, among the two binary splitblocks which are split by the binary block splitting 416 in the verticaldirection, represents an exemplary embodiment in which binary blocksplitting 417 in the horizontal direction is performed again.

The fourth quadtree split block 414 of the block 410 at the uppermostlevel corresponds to the leaf node of the quadtree and represents anexemplary embodiment in which binary block splitting is not performed.

According to the exemplary embodiments, the binary block splittingincludes performing binary splitting or not at the leaf node of thequadtree. However, when the binary splitting is performed, one of thehorizontal binary splitting and the vertical binary splitting isselectively performed. In the block, which is binary-split, additionalbinary splitting may or may not be performed. In addition, when thebinary block splitting is performed at least once, the block which issplit by the corresponding binary block splitting may not be split againusing the quadtree block splitting.

The reference numeral 420 of FIG. 4 illustrates a binary split typeaccording to the directions of the binary block splitting. The binarysplit type may be used interchangeably with terms such as a binary splitdirection, a binary split form, and a binary split type. 0 and 1 may beused to represent that one block is split in one of the horizontal andvertical directions. In the exemplary embodiments, the binary blocksplitting in the vertical direction is shown as 1 and the binary blocksplitting in the horizontal direction is shown as 0.

The reference numeral 430 of FIG. 4 illustrates a binary split index forthe blocks which are binary-split. The binary split index may berepresented using 0 and 1 according to a coding order of the two splitblocks generated by binary splitting of a block at the high level. Thereference numeral 430 of FIG. 4 illustrates an exemplary embodiment inwhich, of two split blocks which are binary-split by using the binarysplit index, the first binary split block is represented by an index 0and the second binary split block is represented by index 1.

FIG. 5 is a drawing illustrating a concept of an MTT block structure, asplit type, and a split block index generated by the binary and triplesplitting according to the exemplary embodiment of the presentinvention.

When a block 510 is split using the MTT block splitting according to theexemplary embodiment, the block 510 may be split into four square blocksby using the quadtree block splitting. In addition, in the MTT blocksplitting, the binary block splitting or the triple block splitting maybe started from the leaf node of the quadtree generated by the quadtreeblock splitting.

In FIG. 5, the first quadtree split block of the block 510 at theuppermost level corresponds to a leaf node of the quadtree andrepresents an exemplary embodiment in which triple block splitting 512and 513 in the horizontal direction are performed. The widths of thethree blocks which are split by performing the triple block splitting512 and 513 in the horizontal direction have the same size N. Theheights of the three blocks which are split by performing the tripleblock splitting 512 and 513 are N/4, N/2, and N/4.

The second quadtree split block of the block 510 at the uppermost levelcorresponds to a leaf node of the quadtree and represents an exemplaryembodiment in which the binary block splitting 514 in the horizontaldirection is performed. The first binary split block of the two binarysplit blocks which are split by performing the binary block splitting514 in the horizontal direction represents an exemplary embodiment inwhich the triple block splitting 515 and 516 in the vertical directionare performed once again. The heights of the three blocks, which aresplit by performing the triple block splitting 515 and 516 in thevertical direction, have the same size M, and the widths of the threeblocks which are split as above have M/4, M/2, and M/4.

The reference numeral 530 of FIG. 5 illustrates a split type accordingto directions of the binary and triple block splitting. The split typemay be used interchangeably with terms such as a binary and triple splitdirection, a binary and triple split form, and a binary and triple splittype. 0 and 1 may be used to represent that one block is split in one ofthe horizontal and vertical directions. In the exemplary embodiment, theblock split in the vertical direction is shown as 1 and the block splitin the horizontal direction is shown as 0.

The reference numeral 550 of FIG. 5 illustrates a split index for theblocks which are binary-split and triple-split. The binary and triplesplit index may be represented using 0, 1, and 2 according to a codingorder of the two split blocks generated by which a block at the highlevel is binary-split. The reference numeral 550 of FIG. 5 illustratesan exemplary embodiment in which, of two split blocks which arebinary-split by using the binary and triple split index, the firstbinary split block is represented by an index 0 and the second binarysplit block is represented by an index 1, and illustrates an exemplaryembodiment in which, of the three split blocks which are triple-split,the first triple split block is represented by an index 0, the secondtriple split block is represented by an index 1, and the third triplesplit block is represented by an index 2.

FIG. 6 is a drawing illustrating an example in which spatial neighboringblocks used in generating a merging candidate list are constructeddifferently according to a split form of a current prediction unitaccording to the exemplary embodiment of the present invention.

The spatial neighboring block to be used in the generation of themerging candidate list according to the exemplary embodiment may have amaximum of five spatial neighboring block candidates A0, A1, B0, B1, andB2 when the size of the current prediction unit is 2N×2N square PU 610.In addition, in generating the merging candidate list, the order inwhich the spatial neighboring block candidates are added to the mergingcandidate list has the order of A1, B1, B0, A0, and B2 as shown in 615of FIG. 6. However, in the case where A1, B1, B0, and A0 are all addedto the spatial merging candidate list according to the maximum number ofspatial neighboring blocks that may be added to the spatial mergingcandidate list, B2 may not be added to the merging candidate list.

The spatial neighboring block to be used in the generation of themerging candidate list according to the exemplary embodiment may have amaximum of four spatial neighboring block candidates A0, A1, B0, B2 whenthe current prediction unit is the second PU 620 of the PUs 620 and 621which are split in the horizontal direction such as 2N×N, 2N×nU, and2N×nD. Compared with that the 2N×2N square PU 610 may have a maximum offive spatial neighboring block candidates A0, A1, B0, B1, and B2, it ispossible to check that B1, which is a neighboring block at the positionabove the current PU 620, has been removed from the spatial neighboringblock candidates. When the current PU 620 is merged with the B1candidate among the merging candidates, PU 621 positioned at the upperend of the current PU 620 is merged therewith. In this case, since thecurrent PU 620 and the PU 621 positioned at the upper end thereof havethe same motion data, the two PUs 620 and 621 have the same meaning asone 2N×2N PU 610. Since the existence of a block having the same meaningcauses a problem in that redundancy of syntax describing a single blockoccurs, the spatial neighboring block candidate of B1 is removed in theprocess of generating the merging candidate list of the second PU 620 ofthe PUs 620 and 621 which are split in the horizontal direction.

The spatial neighboring block to be used in the generation of themerging candidate list according to the exemplary embodiment may have amaximum of four spatial neighboring block candidates A0, B0, B1, and B2when the current prediction unit is the second PU 630 of the PUs 630 and631 which are split in the vertical direction such as N×2N, nL×2N, andnR×2N. Compared with that the 2N×2N square PU 610 may have a maximum offive spatial neighboring block candidates A0, A1, B0, B1, and B2, it ispossible to check that A1, which is a neighboring block at the left sideof the current PU 630, has been removed from the spatial neighboringblock candidates. When the current PU 630 is merged with the A1candidate among the merging candidates, PU 631 positioned at the leftside of the current PU 630 is merged therewith. In this case, since thecurrent PU 630 and the PU 631 positioned at the left side thereof havethe same motion data, the two PUs 630 and 631 have the same meaning asone 2N×2N PU 610. Since the existence of a block having the same meaningcauses a problem in that redundancy of syntax describing a single blockoccurs, the spatial neighboring block candidate of A1 is removed in theprocess of generating the merging candidate list of the second PU 630 ofthe PUs 630 and 631 which are split in the vertical direction.

FIG. 7 is a drawing illustrating an example of a case in which thespatial neighboring blocks used in generating the merging candidate listare identically constructed regardless of the split type of the currentcoding unit according to the exemplary embodiment of the presentinvention.

Unlike the example illustrated in FIG. 6, the example illustrated inFIG. 7 shows about a problem caused by a difference that a block onwhich the current block merging is performed is one independent codingunit (CU) rather than a prediction unit (PU).

In the case where the current coding unit is a coding unit that is notbinary-split, or in the case where the current coding unit is the firstcoding unit of two coding units that are binary-split, a spatialneighboring block used in generating the merging candidate listaccording to the exemplary embodiment may have a maximum of five spatialneighboring block candidates A0, A1, B0, B1, and B2. As in the exampleof the case where the size of the current prediction unit illustrated inFIG. 6 is 2N×2N square PU 610, an example in which up to five spatialneighboring block candidates are provided is shown. Five mergingcandidate blocks A0, A1, B0, B1, and B2, which are spatially adjacentwith the current CU 710 are added to the merging candidate list in theorder of A1, B1, B0, A0, and B2, as shown in 715 of FIG. 7. However, inthe case where A1, B1, B0, and A0 are all added to the spatial mergingcandidate list according to the maximum number of spatial neighboringblocks that may be added to the spatial merging candidate list, B2 maynot be added to the merging candidate list.

FIG. 7 illustrates, in the process of generating the merging candidatelist according to the exemplary embodiment, a problem occurred in casethat the current coding unit has the same spatial neighboring blockcandidates as in the case of the first coding unit of the two codingunits which are binary-split or the coding unit which is notbinary-split. Herein, the current coding unit is the second binary splitcoding unit 720 of the horizontal binary split coding units 720 and 721.

In generating a merging candidate list of the second binary split codingunit 720 of the binary split coding units 720 and 721 in the horizontaldirection according to the exemplary embodiment of FIG. 7, in the casewhere the merging candidate list is generated using a maximum of fivespatial neighboring block candidates A0, A1, B0, B1, and B2 and ismerged with the merging candidate 722 of B1, the second binary splitblock 720 has the same motion data as the first binary split block 721and the two binary split blocks are merged with each other. When the twobinary split blocks 720 and 721 are merged, the two binary split blocks720 and 721 have the same physical meaning as one coding unit 710 whichis unsplit, thereby causing a problem of generating redundancy of syntaxthat describes a single block.

In addition, FIG. 7 illustrates a problem in merging the blocks whichare binary-split in the vertical direction as well as a problem inmerging the blocks which are binary-split in the horizontal direction.FIG. 7 illustrates a problem in that, in generating the mergingcandidate list of the second binary split coding unit 730 of the twocoding units 730 and 731 which are binary-split in the verticaldirection as illustrated in FIG. 7, the second binary split coding unithas the same spatial neighboring block candidates as in the case of thefirst coding unit of the two coding units which are binary-split or thecoding unit which is not binary-split.

In generating the merging candidate list of the second binary splitcoding unit 730 of the coding units 730 and 731 which are binary-splitin the vertical direction according to the exemplary embodiment of FIG.7, when the merging candidate list is generated using a maximum of fivespatial neighboring block candidates A0, A1, B0, B1, and B2 and ismerged with the merging candidate 732 of A1, the second binary splitblock 730 has the same motion data as the first binary split block 731and the two binary split blocks are merged with each other. When the twobinary split blocks 730 and 731 are merged, the two binary split blocks730 and 731 have the same physical meaning as one coding unit 710 whichis unsplit, thereby causing a problem of generating redundancy of syntaxdescribing a single block.

FIG. 8 is a drawing illustrating an example of the spatial neighboringblocks to be used in the merging candidate list of a second binary splitblock among blocks which are binary-split in a horizontal directionaccording to the exemplary embodiment of the present invention.

In generating the merging candidate list of the second binary splitcoding unit of the two binary split coding units in the vertical andhorizontal directions as illustrated in FIG. 7, in order to solve theproblem of having the same spatial neighboring block candidates as inthe case of the first coding unit of the two coding units which arebinary-split or the coding unit which is not binary-split, the exemplaryembodiment proposed by the present invention is illustrated in FIG. 8regarding the spatial neighboring blocks to be used to generate themerging candidate list of the second binary split coding unit among thecoding units which are binary-split in the horizontal direction.

When the second binary split coding unit 720 and the first binary splitcoding unit 721 of the coding units which are binary-split in thehorizontal direction according to the exemplary embodiment have the samesize as shown in FIG. 8, the spatial neighboring block candidates usedin the generation of the merging candidate list of the second binarysplit coding unit 720 of the coding units which are binary-split in thehorizontal direction use A0, A1, B0, and B2, except for the mergingcandidate of B1 which is the neighboring block at the upper end. Thereason why the merging candidates of the neighboring block B1 at theupper end is excluded from the spatial neighboring block candidates isto prevent the merge having the same physical meaning as one coding unitwhich is unsplit.

The condition that the merging candidate of the neighboring block B1 atthe upper end is excluded from the spatial neighboring block candidateincludes: a case in which a current coding unit (CU) for constitutingthe merging candidate list results from binary-splitting in thehorizontal direction; a case in which the current coding unit is asecond binary split coding unit of the coding units which results frombinary-splitting; and a case in which the block width and block heightof the coding unit 721 corresponding to the merging candidate of theneighboring block B1 at the upper end are the same as the block widthand the block height of the current coding unit 720.

A case, in which the block width and the block height of the coding unitcorresponding to the merging candidate of the neighboring block B1 atthe upper end are the same as the block width and the block height ofthe current coding unit, has the same meaning as the case in which thebinary split depth of the coding unit corresponding to the mergingcandidate of the neighboring block B1 at the upper end and the binarysplit depth of the current coding unit are the same, and the above twoexpressions may be used interchangeably. In other words, the descriptionabove means that, in constituting the current merging candidate list ofthe second binary split coding unit, the first binary split coding unitcorresponding to the second binary split coding unit is excluded fromthe spatial merging candidate blocks.

FIG. 8 illustrates spatial neighboring block candidates to be used forgenerating the merging candidate list of the second binary split blockin the case where a first binary split block which results frombinary-splitting in the horizontal direction is split in the verticaldirection or the horizontal direction by additional binary-splitting.

When the first binary split coding unit 721, which results frombinary-splitting in the horizontal direction, is split in the verticaldirection and is composed of two binary split coding units 810 and 811,in constructing the merging candidate list of the second binary splitcoding unit 720 which results from binary-splitting in the horizontaldirection, the merging candidate of B1, which is the neighboring blockat the upper end, is not excluded from the spatial neighboring blockcandidate. The reason is that, even when the first binary split codingunit 721 is split in the vertical direction so that the current codingunit 720 is merged with the target block 811 of the merging candidate722 of B1 which is the neighboring block at the upper end, the mergedresult has a different physical meaning from that of the one coding unitwhich is unsplit.

As in the above exemplary embodiment, when the first binary split codingunit 721, which results from binary-splitting in the horizontaldirection, is split in the horizontal direction and is composed of twobinary split coding units 820 and 821, in constructing the mergingcandidate list of the second binary split coding unit 720 which isbinary-split in the horizontal direction, the merging candidate of B1,which is the neighboring block at the upper end, is not excluded fromthe spatial neighboring block candidate. The reason is that, even whenthe first binary split coding unit 721 is split in the horizontaldirection so that the current coding unit 720 is merged with the targetblock 821 of the merging candidate 722 of B1 which is the neighboringblock at the upper end, the merged result has a different physicalmeaning from that of the one coding unit which is unsplit.

As in the exemplary embodiment in the case where the first binary splitblock, which results from binary-splitting in the horizontal direction,is split in the vertical direction or the horizontal direction byadditional binary-splitting, in generating the merging candidate list ofthe second binary split block which results from binary-splitting in thehorizontal direction, the coding unit corresponding to the mergingcandidate of the neighboring block B1 at the upper end has a block widthand a block height different from the block width and the block heightof the current coding unit, and thus the neighboring block B1 at theupper end is not excluded from the spatial neighboring block candidate.

FIG. 9 is a drawing illustrating an example of the spatial neighboringblocks used in generating the merging candidate list of the secondbinary split block among the blocks which are binary-split in thevertical direction according to the exemplary embodiment of the presentinvention.

When constructing the merging candidate list of the second binary splitcoding unit among the coding units which are binary-split in thevertical and horizontal directions as illustrated in FIG. 7, in order tosolve the problem of having the same spatial neighboring blockcandidates as in the case of the first coding unit of the two codingunits which are binary-split or the coding unit which is binary-unsplit,the exemplary embodiment proposed by the present invention isillustrated in FIG. 9 regarding spatial neighboring blocks to be usedfor generating the merging candidate list of the second binary splitcoding unit among the coding units which are binary-split in thevertical direction.

When the second binary split coding unit 730 among the coding unitswhich results from binary-splitting in the vertical direction and havethe same size as the first binary split coding unit 731 as shown in FIG.9 according to the exemplary embodiment, the spatial neighboring blockcandidates, used in the generation of the merging candidate list of thesecond binary split coding unit 730 among the coding units which resultsfrom binary-splitting in the vertical direction, use A0, B0, B1, and B2,except for the merging candidate of A1, which is the neighboring blockat the left side. The reason why the merging candidates of A1 which isthe neighboring block at the left side is excluded from the spatialneighboring block candidates is to prevent the merge having the samephysical meaning as one coding unit which is unsplit.

The condition that the merging candidate of A1 which is the neighboringblock at the left side is excluded from the spatial neighboring blockcandidates includes: a case in which the current coding unit (CU) forconstituting the merging candidate list results from binary-splitting inthe vertical direction; a case in which the current coding unit is thesecond binary split coding unit among the coding units which resultsfrom binary-splitting; and a case in which the block width and blockheight of the coding unit 731 corresponding to the merging candidate ofA1 which is the neighboring block at the left side are the same as theblock width and the block height of the current coding unit 730.

The case, in which the block width and the block height of the codingunit corresponding to the merging candidate of A1 which is theneighboring block at the left side are the same as the block width andthe block height of the current coding unit, has the same meaning as thecase, in which the binary split depth of the coding unit correspondingto the merging candidate of A1 which is the neighboring block at theleft side and the binary split depth of the current coding unit are thesame. The above two expressions may be used interchangeably. In otherwords, the description above means that, in constituting the currentmerging candidate list of the second binary split coding unit, the firstbinary split coding unit corresponding to the second binary split codingunit is excluded from the spatial merging candidate blocks.

FIG. 9 illustrates spatial neighboring block candidates used forgenerating a merging candidate list of the second binary split blockwhen the first binary split block which is split in the verticaldirection is split in the vertical direction or the horizontal directionby additional binary splitting.

When the first binary split coding unit 731, which results frombinary-splitting in the vertical direction, is split in the horizontaldirection and is composed of two binary split coding units 910 and 911,in constructing the merging candidate list of the second binary splitcoding unit 730 which results from binary-splitting in the verticaldirection, the merging candidate of A1, which is the neighboring blockat the left side, is not excluded from the spatial neighboring blockcandidate. The reason is that, even when the first binary split codingunit 731 is split in the horizontal direction so that the target block911 of the merging candidate 732 of A1, which is the neighboring blockat the left side, is merged with the current coding unit 730, the mergedresult has a different physical meaning from that of the one coding unitwhich is unsplit.

As in the above exemplary embodiment, when the first binary split codingunit 731, which results from binary-splitting in the vertical direction,is split in the vertical direction and is composed of two binary splitcoding units 920 and 921, in constructing the merging candidate list ofthe second binary split coding unit 730 which results frombinary-splitting in the vertical direction, the merging candidate of A1,which is the neighboring block at the left side, is not excluded fromthe spatial neighboring block candidates. The reason is that, even whenthe first binary split coding unit 731 is split in the verticaldirection so that the target block 921 of the merging candidate 732 ofA1, which is the neighboring block at the left side, is merged with thecurrent coding unit 730, the merged result has a different physicalmeaning from that of the one coding unit which is unsplit.

As in the exemplary embodiment in the case where the first binary splitblock, which results from binary-splitting in the vertical direction, issplit in the vertical direction or the horizontal direction byadditional binary splitting, in generating a merging candidate list ofthe second binary split block which results from binary-splitting in thevertical direction, the coding unit corresponding to the mergingcandidate of A1 which is the neighboring block at the left side has ablock width and a block height different from the block width and theblock height of the current coding unit, and thus A1 which is theneighboring block at the left side is not excluded from the spatialneighboring block candidate.

FIG. 10 is a drawing illustrating an example in which a position of thespatial merging candidate block is changed according to a split form ofa first binary split block to generate the merging candidate list of thesecond binary split block among the blocks which results frombinary-splitting in the horizontal direction according to the exemplaryembodiment of the present invention.

In order to generate the merging candidate list of the second binarysplit block 720 among the blocks which results from binary-splitting inthe horizontal direction, the position of the spatial merging candidateblock may be changed according to the split form of the first binarysplit block. FIG. 10 illustrates the exemplary embodiment in which, whenthe first binary split block is split into binary split blocks 810 and811 at the low level through binary splitting in the vertical direction,a reference position of B2 1010 which is a merging candidate at theabove left side of the spatial merging candidates A0, A1, B0, B1, and B2of the current coding unit is changed to B2 1020, which is a mergingcandidate at a position where the first binary split block 810 at thelow level of the binary split blocks at the low level enable to referto.

The position of the merging candidate B2 1010 at the above left side ischanged from (xCb−1, yCb−1) to a position (xCb, yCb−1) of B2 1020 whichis the merging candidate referring to the first binary split block 810at the low level. Here, xCb means the x coordinate position of thecurrent coding block, and yCb means the y coordinate position of thecurrent coding block.

As shown in FIG. 10, in the exemplary embodiment in which a position ofthe spatial merging candidate block used to generate the mergingcandidate list of the second binary split coding unit is changedaccording to the form of the first binary split coding unit, it may bemerged with the binary split coding unit 810 at the low level of thefirst binary split coding unit, by changing the position of one spatialmerging candidate block while maintaining the total number of mergingcandidates to five.

FIG. 11 is a drawing illustrating an example in which the position ofthe spatial merging candidate block is changed according to a split formof the first binary split block to generate the merging candidate listof the second binary split block among the blocks which are binary-splitin the vertical direction according to the exemplary embodiment of thepresent invention.

In order to generate the merging candidate list of the second binarysplit block 730 among the blocks which results from binary-splitting inthe vertical direction, the position of the spatial merging candidateblock may be changed according to the split form of the first binarysplit block. FIG. 11 illustrates the exemplary embodiment in which, whenthe first binary split block is split into binary split blocks 910 and911 at the low level by binary splitting in the horizontal direction, areference position of B2 1110 which is a merging candidate at the aboveleft side of the spatial merging candidates A0, A1, B0, B1, and B2 ofthe current coding unit is changed to B2 1120, which is a mergingcandidate at a position where the first binary split block 910 at thelow level of the binary split blocks at the low level enable to referto.

The position of the merging candidate B2 1010 at the above left side ischanged from (xCb−1, yCb−1) to a position (xCb−1, yCb) of B2 1120 whichis the merging candidate referring to the first binary split block 910at the low level. Here, xCb means the x coordinate position of thecurrent coding block, and yCb means the y coordinate position of thecurrent coding block.

As shown in FIG. 11, in the exemplary embodiment in which a position ofthe spatial merging candidate block used to generate the mergingcandidate list of the second binary split coding unit is changedaccording to the form of the first binary split coding unit, it may bemerged with the binary split coding unit 910 at the low level of thefirst binary split coding unit, by changing the position of one spatialmerging candidate block while maintaining the total number of mergingcandidates to five.

FIG. 12 is a drawing illustrating an example in which the number of thespatial merging candidate blocks is increased according to the splitform of the first binary split block to generate the merging candidatelist of the second binary split block among the blocks which arebinary-split in the horizontal direction according to the exemplaryembodiment of the present invention.

In order to generate the merging candidate list of the second binarysplit block 720 among the blocks which results from binary-splitting inthe horizontal direction, the number of the spatial merging candidateblock may be increased according to the split form of the first binarysplit block. FIG. 12 illustrates the exemplary embodiment in which, whenthe first binary split block is split into binary split blocks 810 and811 at the low level by binary splitting in the vertical direction, anew spatial merging candidate A2 1210 is added to the spatial mergingcandidates A0, A1, B0, B1, and B2 of the current coding unit. The newspatial merging candidate A2 1210 means a merging candidate whoseposition can be referenced by the first binary split block 810 at thelow level among the binary split blocks at the low level.

The position of the new spatial merging candidate A2 1210 indicates aposition referring to the first binary split block 810 at the low levelas (xCb, yCb−1). Here, xCb means the x coordinate position of thecurrent coding block, and yCb means the y coordinate position of thecurrent coding block.

As illustrated in FIG. 12, in the exemplary embodiment in which theposition of the spatial merging candidate block used for generating themerging candidate list of the second binary split coding unit is changedaccording to the form of the first binary split coding unit, it may bemerged with the binary split coding unit 810 at the low level of thefirst binary split coding unit, by increasing the number of mergingcandidates by one.

FIG. 13 is a drawing illustrating an example in which the number of thespatial merging candidate blocks is increased according to the splitform of the first binary split block to generate the merging candidatelist of the second binary split block among the blocks which arebinary-split in the vertical direction according to the exemplaryembodiment of the present invention.

The number of the spatial merging candidate block may be increasedaccording to the split form of the first binary split block in order togenerate the merging candidate list of the second binary split block 730among the blocks which results from binary-splitting in the verticaldirection according to the exemplary embodiment. The exemplaryembodiment illustrated in FIG. 13 shows that, when the first binarysplit block is split into binary split blocks 910 and 911 at the lowlevel through binary splitting in the vertical direction, a new spatialmerging candidate A2 1310 is added to the spatial merging candidates A0,A1, B0, B1, and B2 of the current coding unit. The new spatial mergingcandidate A2 1310 means a merging candidate whose position can bereferenced by the first binary split block 910 at the low level amongthe binary split blocks at the low level.

The position of the new spatial merging candidate A2 1310 is (xCb−1,yCb), indicating a position referring to the first binary split block810 at the low level. Here, xCb means the x coordinate position of thecurrent coding block, and yCb means the y coordinate position of thecurrent coding block.

In the exemplary embodiment in which the position of the spatial mergingcandidate block used for generating the merging candidate list of thesecond binary split coding unit is changed according to the form of thefirst binary split coding unit illustrated in FIG. 13, it may be mergedwith the binary split coding unit 910 at the low level of the firstbinary split coding unit, by increasing the number of merging candidatesby one.

FIG. 14 is a drawing illustrating an example of the spatial mergingcandidate blocks of each of the split blocks among blocks which aretriple-split in the horizontal direction according to the exemplaryembodiment of the present invention.

According to the exemplary embodiment, blocks 1411, 1412, and 1413 whichresults from triple-split in the horizontal direction may have a maximumof five spatial neighboring block candidates A0, A1, B0, B1, and B2. Inaddition, in generating the merging candidate list, the order in whichthe spatial neighboring block candidates are added to the mergingcandidate list has an order of A1, B1, B0, A0, and B2 as shown in 615 ofFIG. 6. However, when A1, B1, B0, and A1 are all added to the spatialmerging candidate list according to the maximum number of spatialneighboring blocks that can be added to the spatial merging candidatelist, B2 may not be added to the merging candidate list.

According to the exemplary embodiment, when the current block among theblocks which results from triple-split in the horizontal direction isthe second block 1422, block merging may be performed using B1positioned at the upper end of the spatial merging candidates. Whenmerging is performed with the block 1421 at the upper end, which is thefirst triple split block, two block split forms having a height of (¾)*Nand (¼)*N may be represented.

According to the exemplary embodiment, when the current block among theblocks which results from triple-split in the horizontal direction isthe third block 1433, block merging may be performed using B1 positionedat the upper end of the spatial merging candidates. When merging isperformed with the block 1432 at the upper end, which is the secondtriple split block, two block split forms having a height of (¼)*N and(¾)*N may be represented.

FIG. 15 is a drawing illustrating an example of the spatial mergingcandidate blocks of each of the split blocks among the blocks which aretriple-split in the vertical direction according to the exemplaryembodiment of the present invention.

According to the exemplary embodiment, blocks 1511, 1512, and 1513 whichresults from triple-split in the vertical direction may have a maximumof five spatial neighboring block candidates A0, A1, B0, B1, and B2. Inaddition, in generating a merging candidate list, the order in which thespatial neighboring block candidates are added to the merging candidatelist has an order of A1, B1, B0, A0, and B2 as shown in 615 of FIG. 6.However, when A1, B1, B0, and A1 are all added to the spatial mergingcandidate list according to the maximum number of spatial neighboringblocks that may be added to the spatial merging candidate list, B2 maynot be added to the merging candidate list.

According to the exemplary embodiment, when the current block among theblocks which results from triple-split in the vertical direction is thesecond block 1522, block merging may be performed using A1 positioned atthe left side of the spatial merging candidates. When merging isperformed with the block 1521 at the left side, which is the firsttriple split block, two block split forms having a height of (¾)*N and(¼)*N may be represented.

According to the exemplary embodiment, when the current block among theblocks which results from triple-split in the vertical direction is thethird block 1533, block merging may be performed using A1 positioned atthe left side of the spatial merging candidates. When merging isperformed with the block 1532 at the left side, which is the secondtriple split block, two block split forms having a height of (¼)*N and(¾)*N may be represented.

FIG. 16 is a flowchart illustrating a removal of the upper end spatialneighboring merging candidate of the second split block among the blockswhich are binary-split in the horizontal direction according to theexemplary embodiment of the present invention.

According to the exemplary embodiment, the generation of the spatialmerging candidate of the second binary split coding unit among thecoding units which results from binary-split in the horizontal directionincludes: a step 1610 of checking whether a binary block split in thehorizontal direction is or not, a step 1620 of checking whether acurrent block is a second split block; a step 1630 of checking equalityof the reference block size at the upper end and the current block size;and a step 1640 of excluding the spatial neighbor merging candidate atthe upper end from the spatial merging candidate list in the case wherethe condition of binary block splitting in the horizontal direction issatisfied and the condition of the second split block is satisfied, andthe size of the reference block at the upper end and the current blockis the same.

In constructing the spatial merging candidate list, in generating thespatial merging candidate of the second binary split coding unit 720among the coding units which results from binary-splitting in thehorizontal direction as shown in FIG. 7, the reference block at theupper end is meant to be a block that includes the position of B1 722.

FIG. 17 is a flowchart illustrating a removal of a spatial neighboringmerging candidate at the left side of a second split block among theblocks which are binary-split in the vertical direction according to theexemplary embodiment of the present invention.

According to the exemplary embodiment, the generation of the spatialmerging candidate of the second binary split coding unit among thecoding units which results from binary-splitting in the verticaldirection includes: a step 1710 of checking whether a binary block splitin the vertical direction is or not; a step 1720 of checking whether acurrent block is a second split block; a step 1730 of checking equalityof the reference block size at the left side and the current block size;and a step 1740 of excluding the spatial neighbor merging candidate atthe left side from the spatial merging candidate list in the case wherethe condition of binary block splitting in the vertical direction issatisfied and the condition of the second split block is satisfied, andthe size of the reference block at the left side and the current blockis the same.

In constructing the spatial merging candidate list, in generating thespatial merging candidate of the second binary split coding unit 730among the coding units which results from binary-split in the verticaldirection as shown in FIG. 7, the reference block at the left side ismeant to be a block that includes the position of A1 732.

FIG. 18 is a drawing illustrating an example of merging blocks thatperform sub-block unit motion compensation among the spatial neighboringblocks used in generating the merging candidate list according to theexemplary embodiment of the present invention.

Unlike the example shown in FIGS. 8 and 9, the example shown in FIG. 18illustrates a method of constructing the merging candidate when aspatial neighboring block merges the blocks performing sub-block unitmotion compensation, even when the current block is the second binarysplit unit which results from binary-splitting in the horizontaldirection or in the vertical direction.

According to the exemplary embodiment of FIG. 18, in generating amerging candidate list of the second binary split coding unit 720 of thecoding units 1821 and 720 which results from binary-splitting in thehorizontal direction, a case of merging a block 1821 at the upper end ofthe spatial neighboring block candidates is illustrated. When the block1821 positioned at the upper end of the current coding unit 720 issubjected to sub-block unit motion compensation, it means that themotion information of the corresponding block 1821 has one or aplurality of different motion information. In other words, the block1821 positioned at the upper end of the current coding unit 720 may bedetermined to be a block in which motion prediction is performed bysplit into a plurality of sub-blocks. As in the case of being furthersplit into the split blocks 810, 811, 820, and 821 as shown in FIG. 8,it may be also interpreted such that the size of the second binary splitcoding unit 720 which is the current coding unit and the size of block1821 positioned at the upper end of the current coding unit 720 aredifferent from each other. Therefore, in generating the spatial mergingcandidate list of the second binary coding unit 720 of the coding units1821 and 720 which results from binary-splitting in the horizontaldirection, even when the block 1821 at the upper end has the same sizeas the current coding unit 720, the merging candidate B1 722 at thecorresponding position may be added to the spatial merging candidatelist in the case where the block 1821 at the upper end is a blockperforming sub-block unit motion compensation.

According to the exemplary embodiment of FIG. 18, in generating amerging candidate list of the second binary split coding unit 730 of thecoding units 1831 and 730 which results from binary-splitting in thevertical direction, a case of merging the block 1831 at the left side ofthe spatial neighboring block candidates is illustrated. When the block1831 positioned at the left side of the current coding unit 730 issubjected to sub-block unit motion compensation, the motion informationof the corresponding block 1831 is meant to have one or a plurality ofdifferent motion information. In other words, the block 1831 positionedat the left side of the current coding unit 730 may be determined to bea block in which motion prediction is performed by split into aplurality of sub-blocks. As in the case of being further split into thesplit blocks 910, 911, 920, and 921 as shown in FIG. 9, it may be alsointerpreted such that the size of the second binary split coding unit730 which is the current coding unit and the size of block 1831positioned at the left side of the current coding unit 730 are differentfrom each other. Therefore, in generating the spatial merging candidatelist of the second binary coding unit 730 of the coding units 1831 and730 which results from binary-splitting in the vertical direction, evenwhen the block 1831 at the left side has the same size as the currentcoding unit 730, the merging candidate A1 732 at the correspondingposition may be added to the spatial merging candidate list in the casewhere the block 1831 at the left side is a block performing sub-blockunit motion compensation.

FIG. 19 is a flowchart illustrating a removal of the spatial neighboringmerging candidate at the upper end of the second split block among theblocks which are binary-split in the horizontal direction according tothe exemplary embodiment of the present invention.

According to the exemplary embodiment, the generation of the spatialmerging candidate of the second binary split coding unit among thecoding units which results from binary-splitting in the horizontaldirection includes: a step 1910 of checking whether a binary block splitin the horizontal direction is or not, a step 1920 of checking whether acurrent block is a second split block; a step 1930 of checking equalityof the reference block size at the upper end and the current block size;a step 1940 of checking whether the reference block at the upper end isa sub-block unit motion compensation block. A step 1950 of excluding thespatial neighbor merging candidate at the upper end from the spatialmerging candidate list is further included in the case where thecondition of the binary block splitting in the horizontal direction issatisfied, in the case where the condition of the second split block issatisfied, in the case where the size of the reference block at theupper end is the same as the size of the current block, and in the casewhere the reference block at the upper end is not the sub-block unitmotion compensation block. Whereas, even when the condition of thebinary block splitting in the horizontal direction is satisfied, thecondition of the second split block is satisfied, and the referenceblock at the upper end and the current block have the same size, thestep 1950 of excluding the spatial neighbor merging candidate at theupper end from the spatial merging candidate list is not included in thecase where the reference block at the upper end is a sub-block unitmotion compensation block.

In constructing the spatial merging candidate list, in generating thespatial merging candidate of the second binary split coding unit 720among the coding units which results from binary-splitting in thehorizontal direction as shown in FIG. 18, the reference block at theupper end is meant to be a block that includes the position of B1 722.

FIG. 20 is a flowchart illustrating a removal of the spatial neighboringmerging candidate at the upper end of the second split block among theblocks which are binary-split in the vertical direction according to theexemplary embodiment of the present invention.

According to the exemplary embodiment, generation of a spatial mergingcandidate of a second binary split coding unit among the coding unitswhich results from binary-splitting in the vertical direction includes:a step 2010 of checking whether a binary block split in the verticaldirection is or not, a step 2020 of checking whether a current block isa second split block; a step 2030 of checking equality of the referenceblock size at the left side and the current block size; a step 2040 ofchecking whether the reference block at the left side is a sub-blockunit motion compensation block. A step 2050 of excluding the spatialneighbor merging candidate at the left side from the spatial mergingcandidate list is further included in the case where the condition ofthe binary block splitting in the vertical direction is satisfied, inthe case where the condition of the second split block is satisfied, inthe case where the size of the reference block at the left side and thesize of the current block are the same, and in the case where thereference block at the left side is not the sub-block unit motioncompensation block. Whereas, even when the condition of the binary blocksplitting in the vertical direction is satisfied, the condition of thesecond split block is satisfied, and the reference block at the leftside and the current block have the same size, the step 2050 ofexcluding the spatial neighbor merging candidate at the left side fromthe spatial merging candidate list is not included in the case where thereference block at the left side is a sub-block unit motion compensationblock.

In constructing the spatial merging candidate list, in generating thespatial merging candidate of the second binary split coding unit 730among the coding units which results from binary-splitting in thevertical direction as shown in FIG. 18, the reference block at the leftside is meant to be a block that includes the position of A1 732.

FIG. 21 is a flowchart illustrating generation of the merging candidatelist according to the exemplary embodiment of the present invention.

According to the exemplary embodiment, a merging candidate listgenerator performing generation of the merging candidate list isconfigured to include: a spatial merging candidate generator 2110; aexamination unit 2120 checking whether to enable to add to a mergingcandidate list; a sub-block unit merging candidate generator 2130; aspatial additional merging candidate generator 2140; a temporal mergingcandidate generator 2150; a bi-directional combined merging candidategenerator 2160; and a zero merging candidate generator 2170.

In generating the merging candidate list according to the exemplaryembodiment, the spatial merging candidate generator 2110 determines amerging candidate that may be addable to the merging candidate listamong spatially adjacent neighboring blocks of the current block, thismeans a method of constructing coding information of spatially adjacentneighboring blocks of the current block into a list. The codinginformation used for merging indicates coding information, whichincludes: motion information of the spatially adjacent neighboringblocks of the current block; prediction direction; index information ofa corresponding reference picture in reference lists according to theprediction direction; and illumination compensation information, whereinmerging the current block with the merging candidate block may beperformed by using the coding information.

The spatial merging candidate generator 2110 using the spatiallyadjacent neighboring blocks of the current block includes: examiningwhether or not the neighboring blocks that are spatially adjacent basedon the current block 710 of FIG. are merged in a certain order; andadding the merging candidate to the merging candidate list whenpossibility of merging is true. The regular order may include using afixed order or using a different order depending on the size of theblock and the split direction of the block. The above step of examiningwhether or not merging is possible is the step that examines whether twodifferent blocks is merged by using coding information of thecorresponding merging candidate and coding information of the currentblock as shown in FIGS. 16, 17, 19, and 20. The coding information ofthe merging candidate and the coding information of the current codingblock may include: whether a coding unit of a merging candidate positionexists; whether the coding unit of the merging candidate positionperforms inter-frame prediction; whether the coding unit of the mergingcandidate position and the current coding block are in different mergeregions. In addition, as the exemplary embodiment shown in FIGS. 16 and17 according to the block split of the current coding unit, the codinginformation of the merging candidate and the coding information of thecurrent coding block may include: binary split direction and whether theblock is binary-split; whether the current coding unit is the secondsplit block; and whether the block size is the same as the upper end orthe left side block according to the split direction. In addition, asthe exemplary embodiment shown in FIGS. 19 and 20, the codinginformation further includes whether the upper end or the left sidereference block, which are currently used as a merging candidate,performs the sub-block unit motion compensation.

In the sub-block unit motion compensation, the reference block splitsone coding unit into a plurality of sub-blocks with a smaller size, thedecoder performs additional motion correction by using motioninformation obtained from the bitstream or motion informationcorresponding to a coding unit generated by the decoder through merging,and performs motion compensation using different corrected motioninformation by the sub-block unit.

INDUSTRIAL APPLICABILITY

The present invention is applicable to the field of high efficiencyimage processing technology.

1-20. (canceled)
 21. An image decoding method performed by an imagedecoding apparatus, the method comprising: splitting a first codingblock into a plurality of second coding blocks according to a tree-basedsplit structure, wherein the tree-based split structure includes atriple-tree split structure; splitting a second coding block into twosub-regions based on block split type information; determining motioninformation of a current sub-region among the two sub-regions from oneof a plurality of merging candidates; and generating a reconstructionsignal by adding a prediction signal to a residual signal, theprediction signal being obtained based on the motion information of thecurrent sub-region, wherein the plurality of merging candidatescomprises at least one of a spatial neighboring merging candidate, atemporal neighboring merging candidate, or a zero motion mergingcandidate, wherein the spatial neighboring merging candidate comprisesat least one of a left neighboring block, a bottom-left neighboringblock, a top-left neighboring block, a top neighboring block or atop-right neighboring block, wherein when the plurality of mergingcandidates comprises the left neighboring block, the bottom-leftneighboring block, the top neighboring block and the top-rightneighboring block, the top-left neighboring block is not added to theplurality of merging candidates, and wherein when the second codingblock is split into the two sub-regions in horizontal directionaccording to the block split type information and the current sub-regionis one of the two sub-regions, a number of the merging candidatesavailable for motion compensation of the current sub-region among thetwo sub-regions is less than a number of merging candidates availablefor motion compensation of the other one of the two sub-regions.
 22. Theimage decoding method of claim 21, wherein the tree-based splitstructure further includes a quad-tree split structure and a binary-treesplit structure, wherein a split according to the binary-tree splitstructure or the triple-tree split structure is started from a leaf nodeof the quad-tree split structure, and wherein when the split accordingto the binary-tree split structure is performed at least once, a blockwhich is split according to the binary-tree split structure is not splitagain according to the quad-tree split structure.
 23. The method ofclaim 21, wherein the triple-tree split structure is a block split ofsplitting, based on two split lines, one coding block into three codingblocks.
 24. The method of claim 23, wherein the two split lines do notcross a center of the one coding block, wherein one of the three codingblocks has a size greater than a size of the other two of the threecoding blocks, wherein the other two of the three coding blocks have thesame size, and wherein the one of the three coding blocks is locatedbetween the other two of the three coding blocks.
 25. An image decodingapparatus comprising: an inter prediction unit splitting a first codingblock into a plurality of second coding blocks according to a tree-basedsplit structure, wherein the tree-based split structure includes atriple-tree split structure, splitting a second coding block into twosub-regions based on block split type information, and determiningmotion information of a current sub-region among the two sub-regionsfrom one of a plurality of merging candidates; and an adder generating areconstruction signal by adding a prediction signal to a residualsignal, wherein the prediction signal is obtained based on the motioninformation of the current sub-region, wherein the plurality of mergingcandidates comprises at least any one of a spatial neighboring mergingcandidate, a temporal neighboring merging candidate, or a zero motionmerging candidate to be added to a merging candidate list, wherein thespatial neighboring merging candidate comprises at least one of a leftneighboring block, a bottom-left neighboring block, a top-leftneighboring block, a top neighboring block or a top-right neighboringblock, wherein when the plurality of merging candidates comprises theleft neighboring block, the bottom-left neighboring block, the topneighboring block and the top-right neighboring block, the top-leftneighboring block is not added to the plurality of merging candidates,and wherein when the second coding block is split into the twosub-regions in horizontal direction according to the block split typeinformation and the current sub-region is one of among the twosub-regions, a number of the merging candidates available for motioncompensation of the current sub-region among the two sub-regions is lessthan a number of merging candidates available for motion compensation ofthe other one of the two sub-regions.
 26. An image encoding methodperformed by an image encoding apparatus, the method comprising:splitting a first coding block into a plurality of second coding blocksaccording to a tree-based split structure, wherein the tree-based splitstructure includes a triple-tree split structure; splitting the secondcoding block into two sub-regions; and generating a residual signal bysubtracting a prediction signal from an original signal, the predictionsignal being obtained based on motion information of a currentsub-region among the two sub-regions, wherein the motion information ofthe current sub-region is determined from one of a plurality of mergingcandidates, wherein the plurality of merging candidates comprises atleast one of a spatial neighboring merging candidate, a temporalneighboring merging candidate, or a zero motion merging candidate,wherein the spatial neighboring merging candidate comprises at least oneof a left neighboring block, a bottom-left neighboring block, a top-leftneighboring block, a top neighboring block or a top-right neighboringblock, wherein when the plurality of merging candidates comprises theleft neighboring block, the bottom-left neighboring block, the topneighboring block and the top-right neighboring block, the top-leftneighboring block is not added to the plurality of merging candidates,and wherein when the second coding block is split into the twosub-regions in horizontal direction and the current sub-region is one ofthe two sub-regions, a number of the merging candidates available formotion compensation of the current sub-region among the two sub-regionsis less than a number of merging candidates available for motioncompensation of the other one of the two sub-regions.